They are met with in general in almost all the moveable articulations,
and especially upon their sides; hence the name of lateral ligaments
by which most of them are designated. Some however are foreign to the
articulations, as we see an example in that extending from the coracoid
to the acromion process, in those which complete the different osseous
fissures, the orbitary for example.
These organs form fasciæ sometimes round, sometimes flat, fixed to, or
rather intermixed with the periosteum by their two extremities, easily
removed with it in childhood, holding to the bone in the adult by the
ossification of the internal layers of this membrane.
Their analogy with the tendons is very striking; the external
difference is that they hold to the periosteum at both sides, whilst on
one side the tendons are contiguous with the muscles. We see sometimes
that the same organ is a tendon at one age, and a ligament at another.
This arrangement is remarkable in the inferior ligament of the patella.
Yet there are, as we have remarked, differences of composition between
them. All result from an assemblage of fibres parallel in the middle,
diverging at the extremities, united by a cellular texture more loose
than that of the tendons, and which often contains some fatty flakes.
This substance is sometimes so abundant in them, that they have an
appearance analogous to that of the fatty muscles; I have made this
observation on the ligaments of the knee, in a subject elsewhere very
thin.
There are some blood vessels in the ligaments. In certain diseases
of the articulations, their vascular system is developed in a very
remarkable manner, and they are penetrated by a great quantity of
blood; no nerve is discoverable in them.
Sometimes the ligamentary texture is changed into a matter like lard,
in which every kind of fibre disappears, which rarely returns to
its primitive state, and which is met with almost always in organic
affections, fatal to the patient.
The ligaments unite strongly the osseous surfaces, prevent their
displacement, and yet allow easy motions; a double function which they
perform in virtue of a double property, of their resistance on the
one part, of their softness and flexibility on the other; sometimes
externally, they serve for some muscular insertions.